Experimental considerations in the quest for a thin-film superconducting field-effect transistor

Trilayer structures, comprising a thin-film In/InOxsuperconductor separated from an Al gate electrode by an overgrown dielectric, have been studied to ascertain the feasibility of electric-field control of superconductivity for device applications, Modulation of the areal charge density of 50-Å thick In/InOxfilms has been found to cause more than a 350Ω/ change in the sheet resistance near the midpoint of the resistive transition in one film and the creation of ~10Ω/ of resistance from the superconducting state of a second film. We report on efforts to increase this modulation by decreasing the electron density of unperturbed films, improving the charge storage capabilities of the thin-film gate dielectrics, and improving the carrier mobility which has been found to be sensitive to interface preparation. Device implications, based on these results, are also discussed.